Include a "stack trace" with nested-import errors (#1872)

* Include a "stack trace" with nested-import errors

When errors occur in nested `#include` files it is often helpful to have a "stack trace" / traceback of the `#include` chain that led from a root translation unit to the file with an error.

This change implements a similar feature for `import`s.

It is worth noting that `import`s don't really *require* this kind of compiler support the way `#include`s do because the intention is that the meaning of an `import`ed file does not depend on the order or nesting of `import`s. As such, when trying to *fix* an error in an `import`ed file, you usually don't care how it came to be `import`ed into your shaders.

The use case here is somebody adapting a large body of Slang code to use in a different codebase, such that they have certain `.slang` files they don't actually intend to have compile correctly, and they want to be able to diagnose how they came to include those files when/if they cause problems.

The actual feature implementation is pretty simple because we already track a stack of active `import`s so that we can detect and diagnose recursive `import`s. This change simply changes the disagnostics when there is an error in imported code so that instead of just noting the inner-most `import` site it lists all the `import` sites that were active at the time.

The change includes a test case to confirm that the behavior works (at least for the case of a parse error).

* fixup: test outputs

Co-authored-by: Yong He <yonghe@outlook.com>
Co-authored-by: jsmall-nvidia <jsmall@nvidia.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/source/slang/slang.cpp b/source/slang/slang.cpp
index 9d2d766b9..f8af39fcb 100644
--- a/source/slang/slang.cpp
+++ b/source/slang/slang.cpp
@@ -2397,6 +2397,15 @@ Module* Linkage::loadModule(String const& name)
         sink);
 }
 
+void Linkage::_diagnoseErrorInImportedModule(
+    DiagnosticSink*     sink)
+{
+    for(auto info = m_modulesBeingImported; info; info = info->next)
+    {
+        sink->diagnose(info->importLoc, Diagnostics::errorInImportedModule, info->name);
+    }
+    sink->diagnose(SourceLoc(), Diagnostics::complationCeased);
+}
 
 RefPtr<Module> Linkage::loadModule(
     Name*               name,
@@ -2418,7 +2427,9 @@ RefPtr<Module> Linkage::loadModule(
 
     ModuleBeingImportedRAII moduleBeingImported(
         this,
-        module);
+        module,
+        name,
+        srcLoc);
 
     // Create with the 'friendly' name
     SourceFile* sourceFile = getSourceManager()->createSourceFileWithBlob(filePathInfo, sourceBlob);
@@ -2431,7 +2442,7 @@ RefPtr<Module> Linkage::loadModule(
 
     if( errorCountAfter != errorCountBefore )
     {
-        sink->diagnose(srcLoc, Diagnostics::errorInImportedModule);
+        _diagnoseErrorInImportedModule(sink);
     }
     if (errorCountAfter)
     {
@@ -2449,7 +2460,7 @@ RefPtr<Module> Linkage::loadModule(
 
     if (errorCountAfter != errorCountBefore)
     {
-        sink->diagnose(srcLoc, Diagnostics::errorInImportedModule);
+        _diagnoseErrorInImportedModule(sink);
         // Something went wrong during the parsing, so we should bail out.
         return nullptr;
     }